Grazing incidence vacuum spectrometer housing structure



Dec. 13, 1966 E. ALEXANDER ETAL 3,291,982

GRAZING INCIDENCE VACUUM SPECTROMETER HOUSING STRUCTURE Filed March 31,1966 2 Sheets-Sheet 1 Dec. 13, E, ALEXANDER ET AL 3,291,982

GRAZING INCIDENCE VACUUM SPECTROMETER HOUSING STRUCTURE Filed March 31,1966 2 Sheets-Sheet 2;

Q li if 1NVENTOR. ERNS T A L EXANDER BENJAMIN .5. F94 ENKEL BY afgfilw ATI'ORNE'KSI United States Patent 7 Claims. b1. 250-515 This applicationis a continuationdn-part of application Ser. No. 271,783, filed Apr. 9,1963, now abandoned, for Grazing Incidence Vacuum Spectrometer.

The present invention relates to vacuum spectrometers and, moreparticularly, to a novel vacuum spectrometer having a high accuracy anda high spectra resolution, and in which all of the movable optical partsof the spectrometer, disposed within a high vacuum, sealed container,are mounted fixedly on one common point of the container, whereby anychange of the dimension of the container will have no effect on thegeometry of the optical system of the spectrometer.

While the first-order spectra are obtainable with a considerableresolution, enabling, over a wide range, the determination of wavelengths up to an accuracy better than 0.01 Angstrom, there are caseswhere a much higher resolution is needed. This requires, for example, anaccurately constructed spectrometer having a wide range, with rigidityof the mounting of movable parts as well as flexibility in adjustmentand operation. Furthermore, it is desirable that these conditions be metin a spectrometer which is not too great in size and preferably has asize not greater than spectrometers having less accuracy and a smallerrange of resolution.

An object of the present invention is to provide a vacuum spectrometerof high accuracy.

Another object of the invention is to provide a vacuum spectrometerwhich can be used over a wide range of frequencies.

A further object of the invention is to provide a spectrometer adaptedto provide accurate measurements over a substantial range of short wavelengths.

Yet another object is to provide means for effecting measurements ofmultiply ionized atoms and for comparing intensities of diiferentspectra as a function of various parameters.

Yet a further object of the invention is to provide a vacuumspectrometer of relatively simple construction, which will not beaffected, as to accuracy of measurements, by changes of the sealedcontainer due to changes in pressure.

With these considerations in mind, the present invention relates to agrazing incidence vacuum spectrometer comprising the combination of avacuum-tight housing, adapted to withstand a high internal vacuum, andan axle assembly extending into the housing, in vacuum sealed relation,through an opening thereof and supporting, within the housing, twoswingable arms extending at right angles from the axis of the axleassembly and positioned axially closely adjacent each other. The freeend of one of these arms supports a suitable diffraction grating, of agiven radius of curvature, and a slit system. The free end of the otherarm supports a plate holder by means of which the plate is located on aRowland circle having a radius of curvature half that of the diffractiongrating. Other elements of the slit system extend, by means of aflexible bellows, in vacuumtight relation through a second openingprovided in the housing, and means are provided for establishing andmaintaining a suitable vacuum within the housing.

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Means are provided for turning the arm supporting the plate holder, froma position outside of the container, and other means are provided formoving the plate parallel to the supporting axis of its arm so as toenable the making of a number of consecutive exposures on the same platewithout breaking the vacuum.

The diffraction grating preferably is angularly adjustable within apredetermined range so as to enable the obtaining of a range of anglesof incidence of the radiation to be measured, which is introducedthrough the slit system into the housing.

The supporting axle means and the arms attached thereto are rigid and ofsubstantial dimensions, whereby a high degree of accuracy is easilyobtained.

As the source of radiation to be measured, there may be used a source ofsoft X-rays or a spark chamber. The desired radiation is introduced, asmentioned, into the housing through a window or opening so as to impingeon the grating at a predetermined angle of incidence. The radiation isfocused, after diffraction, on'the Rowland circle, where the diffractionradiation can be determined after exposure of the photographic platelocated in the plane defined by the Rowland circle.

With the apparatus of the invention, measurements can be madeeffectively at a vacuum of about 10* mm. Hg in the housing of thespectrometer. When a spark chamber is used as a source of radiation, itis advantageous to use a vacuum of about 10- mm. Hg in the sparkchamber, and the vacuum of the spectrometer can be used as thefore-vacuum of the spark chamber or X-ray tube.

For an understanding of the principles of the invention, reference ismade to the following description of a typical embodiment thereof asillustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a somewhat schematic plan spectrometer;

FIG. 2 is a front elevation view of the spectrometer, partly broken awayand in section;

FIG. 3 is a side elevation view of the spectrometer;

FIG. 4 is a partial perspective view of the interior of thespectrometer; and

FIG. 5 is a sectional view illustrating the slit system and anassociated spark chamber.

The vacuum container 1 of the spectrometer is made of two parts, namelya fixed part 2 and a removable lid or cover 3. The fixed part has anopening 23 from which there extends a relatively heavy suport sleeve 24,the major portion of support sleeve 24 extending inwardly from opening23 and a shorter portion thereof extending outwardly therefrom. An axleassembly or cone 25 is angularly adjustably mounted within bushing orsleeve 24.and comprises telescoped male and female parts extending fromexternally of container 20 to a point internally thereof. The femaleelement 25A of cone 25 supports, at its lower or inner end, a horizontalarm 7, to the free end of which are attached the grating holder 9, andthe slit system generally indicated at 11. The plate holder 12, or,alternatively, a multiplier, are attached to the male part 25B of cone25 -by means of a second horizontal arm 8 which has a range of movementthrough an angle of The male and female parts of come 25 are telescoped,and the center of the Rowland circle lies on the vertical axis AAdefined by the cone 25.

The sleeve 24, in conjunction with the opening 23 through which itextends, constitutes a firm vacuum-tight support for the movableelements of the optical system, particularly the arms 7 and 8. Asstated, the arm 7 supports, at its free end, a grating 9 which is aSiegba-hn grating of substantially 30,000 lines per inch, and having aradius of curvature of Z'rneters.

view of the As best seen in FIGS. 4 and S, the hollow horizontal arm 7extending from the female part of the cone 25, supports, near its freeend, an adjustable sleeve 26. This sleeve supports the slit system,generally indicated at 11, and the grating holder 9. The grating holderis built in such a manner that the grating is angularly adjustable aboutthree perpendicular axes intersecting at the central point of thesurface of the grating, and is also movable along three mutuallyperpendicular directions. system is physically connected with thecontainer by a flexible bellows 10 so as to permit movement whilemaintaining the vacuum within the container. Means are provided formoving the slit system 11 grating so that it will make a predeterminedgrating angle of between about 1 and about 10 with the diffractiongrating.

The slit system 11, as best seen in FIG. 5, comprises a main slit 20which is at a distance from the center of the grating, for a grazingincidence angle of and a Rowland circle of 1 mm. radius, of about 17.5cm. A secondary slit 14 which, under the given conditions, is 3 cm. fromthe center of the grating, is incorporated with the main slit 20 intothe slit system 4 and the slits are joined together by a 12 diameterstainless steel tube 15 about 14.5 cm. in length. The secondary slit 14is interchangeable with similar slits, of various widths, and the widthof the secondary slit determines the width of the area of the gratingparticipating in reflection. This width may therefore be changedaccording to the optimal width correlated to the wave length range beinginves-' tigated. The slit system extends through an opening 27 throughthe housing, which is sealed vacuum-tight by the bellows 10, and theopening 27 leaves room for changing the grazing incidence angle fromabout 1 to about This change can be performed by rotating the slitsystem about an axis through the central point of the grating, parallelto the main axis of the instrument. Adjustment about another axisprovides for the slit system to be adjusted to point to the center ofthe grating.

Referring to FIG. 5, a sot-t X-ray tube or spark chamber 30 provides thesource of radiation, and a tube or conduit 31 leads therefrom to anevacuating system. An adjustable bellows system 32 connects the X-raytube or spark chamber to a collar 33 aligned with the opening 27.

Referring again to FIG. 5, it should be noted that a vacuum ismaintained both inside and outside the bellows 10, as the interior ofthis bellows is subjected to the vacuum within the container of thespectrometer and the exterior thereof is subjected to the vacuum in thespark chamber or soft X-ray tube. Thereby, the vacuum ditference betweenthe spark chamber or soft X-ray tube and the interior of the casing ofthe spectrometer is governed by the slit opening only and not by theopening of the hole through which the slit system extends into the body.

The plate holder 12 is essentially a stainless steel frame ground to aradius of curvature of 1 meter and built, for example, to hold 10 x 2inch thin glass plate 13. The plate holder 12, as stated is mounted onthe angularly displaceable arm 8 extending from the male part 253 ofcone 25. The plate holder may be elevated, in a direction parallel toaxis AA, so that seven difierent exposures may be taken on the film eachabout 5 mm. wide. Also, as best seen from FIG. 1, the plate holder maybe moved on the Rowland circle from a position adjoining the grating toa position at an :angle of about 90 with the grating. Both movements maybe effected from outside the casing of the spectrometer by rotating thepart 25B at the protruding upper end thereof. The elevating wave lengthranges may be made without breaking the vacuum within the instrument.

The slit The plate 12 can be adjusted radially with respect to axis AAin a very accurate manner, up to 0.01 millimeter. With the two arms 7and 8 aligned, an indicator can be placed on arm 7 and the exactdistance from axis AA can be noted by putting the tip of the indicatoron film 13 in plate holder 12. The arm 8 is then swung about its axisand the indicator used to measure the distance of grating 9 from theaxis AA is the same as the reading of the previously adjusted plate 13and plate holder 12.

As both arms 7 and 8 are, in elfect, adjustable about the same axis AA,and due to the provision of the flexible bellows 10, possible changes ofthe dimension of the container 1 due to differences of pressure will notadversely affect the accuracy of the measurements.

A third opening is provided in the casing or container of thespectrometer and has attached thereto, in vacuumtight relation, a duct35 which is connected to a vacuum pump, such as a 300 liter per second 4inch diffusion pump. The spectrometer serves as a fore-vacuum containerfor the X-ray tube, which is additionally evacuated by a 60 liter persecond 2 inch diffusion pump connected to the duct 31. Furthermore, a450 liter per minute single-stage rotary vacuum pump is used as a forepump.

With the vacuum spectrometer of the invention, its possible toinvestigate short wave lengths with great accuracy by using high ordersof diffraction. For example, the line 192,906 A. of 0 v. was observed inthe 11th order. We found that with the accuracy of ad justment up to0.01 mm. of the Optical geometry on the Rowland circle, and with theangle of turning of 90 of the arm supporting the plateholder, a spectralrange of from 90 A. to 2,300 A. could be investigated with a highresolution.

The spectrometer is operated at a vacuum of about 10* mm. Hg in thehousing 1 and the radiation is introduced through the slit system 10.When a soft X-ray tube or a spark chamber is used as source ofradiation, such source is advantageously operated at a pressure of about10* mm. Hg. In this case it is advantageous to use the vacuum of thehousing 1 as fore-vacuum of the source of radiation.

Although a specific embodiment of the invention has been shown anddescribed in detail to illustrates the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. A grazing incidence vacuum spectrometer comprising, in combination, avacuum-tight housing adapted to withstand a high internal vacuum; asleeve extending in vacuum-tight relation through an opening in saidhousing; a pair of axles extending rotatably through said sleeve invacuum-tight relation therein, said axles being concentric with saidsleeve and one of said axles being a tubular axle and the other axleextending through said tubular axle in telescoped relation therewith; apair of arms within said housing, each secured to the inner end of arespective one of said axles and extending radially from the associatedaxle, said arms being positioned closely adjacent each other axially ofsaid axles; said axles providing for independent angular adjustment ofsaid two arms about the common axis of said axles; a diffractiongrating, having a preselected radius of curvature, and a slit systemsupported at the free end of one of said arm; a photographic plateholder supported on the free end of the other arm, a photographic platethereon being positioned on the Rowland circle having half the radius ofcurvature of the diffraction grating; said diffraction grating and saidplate holder being disposed at substantially the same radius from thecommon axis of said axles whereby a photographic plate on said plateholder may .be brought into substantial coincidence with saiddiffraction grating; a source of radiation under a relatively highvacuum in operative connection with the external end of said slit systemfor directing radiation through said slit system to impinge on saidgrating; said slit system extending through another opening in saidcasing; a bellows in vacuum-tight connection to said casing and to saidslit system and subjected on its interior to the vacuum in said housingand on its exterior to the vacuum of said source of radiation; and meansfor establishing and maintaining a substantial vacuum in said housing;whereby, the optical system of said spectrometer is supported from asingle point which is said sleeve and said two axles, so that theinterrelation of the optical parts is not effected by changes indimension of the housing.

2. A vacuum spectrometer, as claimed in claim 1, in which said slitsystem includes a relatively elongated tube extending through saidbellows and having slits, one at the outer end thereof and the other atthe inner end thereof, said tube being supported on said one arm andsaid one arm being adjustable through a relatively limited angle.

3. A vacuum spectrometer, as claimed in claim 1, said diffractiongrating being adjustable on the free end of said one arm about threemutually perpendicular axes to adjust the angle of incidence of theradiation on said grating within a preselected limit.

4. A vacuum spectrometer, as claimed in claim 1, wherein the angle ofincidence of the radiation impinging upon said grating is adjustablebetween an angle of from 1 to 10.

5. A vacuum spectrometer, as clarned in claim 1, wherein said other armsupporting said plate holder is adjustable through an angle in excess of6. A vacuum spectrometer, as claimed in claim 1, including means foradjusting said plate holder transversely of said other arm and in adirection parallel to said common axis, whereby a plurality ofconsecutive exposures can be made on one photographic plate on saidplate holder.

7. A vacuum spectrometer, as claimed in claim 1, wherein the vacuum ofsaid housing serves as a forevacuum for external source of radiation,under a high No references cited.

RALPH G. NILSON, Primary Examiner.

ANTHONY L. BIRCH, Assistant Examiner.

1. A GRAZING INCIDENCE VACUUM SPECTROMETER COMPRISING, IN COMBINATION, AVACUUM-TIGHT HOUSING ADAPTED TO WITHSTAND A HIGH INTERNAL VACUUM; ASLEEVE EXTENDING IN VACUUM-TIGHT RELATION THROUGH AN OPENING IN SAIDHOUSING; A PAIR OF AXLES EXTENDING ROTATABLY THROUGH SAID SLEEVE INVACUUM-TIGHT RELATION THEREIN, SAID AXLES BEING CONCENTRIC WITH SAIDSLEEVE AND ONE OF SAID AXLES BEING A TUBULAR AXLE AND THE OTHER AXLEEXTENDING THROUGH SAID TUBULAR AXLE IN TELESCOPED RELATION THEREWITH; APAIR OF ARMS WITHIN SAID HOUSING, EACH SECURED TO THE INNER END OF ARESPECTIVE ONE OF SAID AXLES AND EXTENDING RADIALLY FROM THE ASSOCIATEDAXLE, SAID ARMS BEING POSITIONED CLOSELY ADJACENT EACH OTHER AXIALLY OFSAID AXLES; SAID AXLES PROVIDING FOR INDEPENDENT ANGULAR ADJUSTMENT OFSAID TWO ARMS ABOUT THE COMMON AXIS OF SAID AXLES; A DIFFRACTIONGRATING, HAVING A PRESELECTED RADIUS OF CURVATURE, AND A SLIT SYSTEMSUPPORTED AT THE FREE END OF ONE OF SAID ARM; A PHOTOGRAPHIC PLATEHOLDER SUPPORTED ON THE FREE END OF THE OTHER ARM, A PHOTOGRAPHIC PLATETHEREON BEING POSITIONED ON THE ROWLAND CIRCLE HAVING HALF THE RADIUS OFCURVATURE OF THE DIFFRACTION GRATING; SAID DIFFRACTION GRANTING AND SAIDPLATE HOLDER BEING DISPOSED AT SUBSTANTIALLY THE SAME RADIUS FROM THECOMMON AXIS OF SAID AXLES WHEREBY A PHOTOGRAPHIC PLATE ON SAID PLATEHOLDER MAY BE BROUGHT INTO SUBSTANTIAL COINCIDENCE WITH